Kefir extracts suppress in vitro proliferation of estrogen-dependent human breast cancer cells but not normal mammary epithelial cells.

Anti-tumorigenic effects have been demonstrated in animal studies from the intake of kefir, a traditional fermented milk product believed to originate from the Caucasian mountains of Russia. In the present study, the antiproliferative effects of extracts of kefir, yogurt, and pasteurized cow's milk on human mammary cancer cells (MCF-7) and normal human mammary epithelial cells (HMECs) was investigated at doses of 0.31%, 0.